Variable air intake system

ABSTRACT

A valve closing side engaging groove is formed in a circumferential surface of a collar of a clutch between an optimum angular position, which implements a most effective valve angle for making the maximum fuel consumption improving effect, and a valve closing side least effective angular position, which implements a valve closing side least effective valve angle. Similarly, a valve opening side engaging recess is formed in the circumferential surface of the collar between the optimum angular position and a valve opening side least effective angular position, which implements a valve opening side least effective valve angle. Each of the grooves is engageable with a roller to securely hold the roller in corporation with a driven-side rotator to limit rotation of the driven-side rotator in a deenergized state of a motor.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2008-38882 filed on Feb. 20, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable air intake system, which includes a clutch that enables transmission of a rotational force of an electric motor toward a valve and disables transmission of a rotational force of the valve toward the electric motor.

2. Description of Related Art

In a known variable air intake system, a valve is placed in an air intake passage of an internal combustion engine (hereinafter, referred to as an engine). An opening degree of the valve is held in an intermediate opening degree of the valve to generate, for example, a tumble flow or swirl flow in a combustion chamber of the engine to improve a combustion state of fuel in the combustion chamber. Thereby, purification of exhaust gas of the engine at the time of engine start can be improved, and the fuel consumption improving effect can be enhanced.

In the above-described technique, the opening degree of the valve is held constant at the time of implementing the above effects, and this opening degree of the valve is maintained through the energization of the electric motor. Thus, the electric power is required to maintain the opening degree of the valve as long as the engine is operated.

In order to minimize the electric power consumption, it is conceivable to use a clutch, which conducts a rotational force from a driving-side rotator to a driven-side rotator and does not conduct a rotational force from the driven-side rotator to the driving-side rotator while transmitting such a rotational force to a collar (serving as a stationary member). With this clutch, the energization of the motor can be stopped at the time of maintaining the opening degree of the valve. For example, WO 00/08349A1 (corresponding to U.S. Pat. No. 6,575,277B1), WO 00/08350A1 (corresponding to U.S. Pat. No. 6,789,443B1) and JP 2001-214946A teach various types of clutches.

In the case of the WO 00/08349A1 (corresponding to U.S. Pat. No. 6,575,277B1) or WO 00/08350A1 (corresponding to U.S. Pat. No. 6,789,443B1), the collar is placed radially outward of the driven-side rotator. In contrast, in the case of JP 2001-214946A, the collar is placed radially inward of the driven-side rotator.

However, in the case of the clutch recited in WO 00/08349A1 (corresponding to U.S. Pat. No. 6,575,277B1), WO 00/08350A1 (corresponding to U.S. Pat. No. 6,789,443B1) or JP 2001-214946A, the clutch is used in a power window system of a vehicle. When such a clutch is used for the valve of the variable air intake system, a pressure pulsation, which occurs in the intake passage, causes application of a rotational force (specifically, a rotational force caused by large vibration, large load, large pressure pulsation or the like) to the valve, so that the holding state of the valve (the engaged state of the clutch) may possibly be released. That is, the rotation of the valve cannot be limited by the clutch.

In view of the above disadvantage, a plurality of recesses may be provided in an engaging surface of the collar, to which rollers are locked. The rollers are fitted into the corresponding recesses of the collar, so that the holding force (the engaging force of the clutch) for holding the valve in place is improved. Therefore, even when the rotational force is applied to the valve due to the pressure pulsation, the holding state of the valve is not unintentionally released. This technique is recited in, for example, JP 2007-198584A (corresponding to US 200710144854A1).

In the case of JP 2007-198584A (corresponding to US 2007/0144854A1), the recesses are provided in the collar to increase the holding force for holding the valve. However, the locations of the recesses are not set to maintain an effective opening degree range of the valve, which enables the improvement of the fuel consumption.

Specifically, in the case of the variable air intake system, the opening degree of the valve needs to be maintained within the effective opening degree range shown, for example, in FIG. 6 (the opening degree range of the valve, in which the fuel consumption improving effect is larger than zero and is indicated as “required accuracy” in FIG. 6), which enables the improvement of the fuel consumption of the engine. However, in the previously proposed techniques discussed above, the above point is not concerned.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantage. According to the present invention, there is provided a variable air intake system for an internal combustion engine. The variable air intake system includes an electric motor, a valve and a clutch. The electric motor is rotated to generate a rotational force in an energized state of the electric motor. The valve is placed in an air intake passage of the internal combustion engine and is rotated by the rotational force transmitted from the electric motor to adjust intake air supplied to the internal combustion engine through the air intake passage. The clutch is placed between the electric motor and the valve to enable transmission of the rotational force from the electric motor to the valve and to disable transmission of a rotational force from the valve to the electric motor. The clutch includes a driving-side rotator, a driven-side rotator, an annular collar and an engageable element. The driving-side rotator is rotated by the rotational force transmitted from the electric motor and includes a plurality of circumferential side engagement releasing projections, each of which circumferentially projects from a corresponding adjacent part of the driving-side rotator that is adjacent to the circumferential side engagement releasing projection. The driven-side rotator is coaxial with the driving-side rotator and is rotated by the driving-side rotator upon circumferential engagement with the driving-side rotator to rotate the valve in the energized state of the electric motor. The annular collar is non-rotatably held and has a circumferential surface, which is coaxial with the driven-side rotator, wherein a radial gap is formed between an engaging portion of the driven-side rotator and the circumferential surface of the collar and includes first and second circumferential side gap sections and a circumferentially intermediate gap section, which are arranged in such a manner that the circumferentially intermediate gap section is circumferentially placed between the first and second circumferential side gap sections and has a radial size larger than a radial size of any of the first and second circumferential side gap sections. The engageable element is circumferentially placed between the first and second circumferential side gap sections in the radial gap. A radial size of the engageable element is smaller than the radial size of the circumferentially intermediate gap section and is larger than the radial size of any of the first and second circumferential side gap sections, and the engageable element is circumferentially displaceable by a corresponding one of the plurality of circumferential side engagement releasing projections at a time of driving the driven-side rotator by the driving-side rotator.

The clutch and the valve are synchronized to satisfy all of the following conditions. That is, when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to place the engageable element in a first angular position along the circumferential surface of the collar, the valve is placed in a most effective valve angle, at which a fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is maximized. Also, when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to displace the engageable element in a first circumferential direction from the first angular position to a second angular position along the circumferential surface of the collar, the valve is rotated in a valve closing direction from the most effective valve angle to a valve closing side least effective valve angle, at which the fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is reduced to zero. Furthermore, when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to displace the engageable element in a second circumferential direction, which is opposite from the first circumferential direction, from the first angular position to a third angular position along the circumferential surface of the collar, the valve is rotated in a valve opening direction from the most effective valve angle to a valve opening side least effective valve angle, at which the fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is reduced to zero.

A valve closing side engaging recess is formed in the circumferential surface of the collar between the first angular position and the second angular position and is engageable with the engageable element to securely hold the engageable element in cooperation with the engaging portion of the driven-side rotator in the de-energized state of the electric motor. A valve opening side engaging recess is formed in the circumferential surface of the collar between the first angular position and the third angular position and is engageable with the engageable element to securely hold the engageable element in cooperation with the engaging portion of the driven-side rotator in the de-energized state of the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a diagram showing a valve angle of a valve and an angular position of a roller along a collar of a clutch with respect to a fuel consumption improving rate according to an embodiment of the present invention;

FIG. 2A is a schematic view showing the clutch according to the embodiment;

FIG. 2B is a partial enlarged view showing the roller held in a groove of the collar in the clutch;

FIG. 3A is a perspective view showing an electric motor, the clutch and a speed reducer according to the embodiment;

FIG. 3B is a schematic cross sectional view showing the clutch received in a clutch housing;

FIG. 4 is a diagram showing a relationship between a fuel consumption deteriorating rate caused by a pumping loss and an opening degree of the valve according to the embodiment;

FIG. 5 is a diagram showing a relationship between a fuel consumption improving rate caused by EGR and an opening degree of the valve according to the embodiment;

FIG. 6 is a diagram showing a relationship between a fuel consumption improving rate and an opening degree of the valve according to the embodiment; and

FIG. 7 is a schematic view showing the valve placed in an air intake passage according to the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described with reference to FIGS. 1 to 7.

With reference to FIG. 7, a variable air intake system of the present embodiment is a system that changes an opening degree of a valve 100, which is placed in an air intake passage 111 of an internal combustion engine. The valve 100 has a hinged valve structure and thereby has a plate-shaped opening and closing member (valve plate) 100 a and a valve drive shaft 100 b. The valve drive shaft 100 b extends through a lower end portion of the opening and closing member 100 a. More specifically, each corresponding opening and closing member 100 a is placed in the air intake passage 111 of a corresponding one of tubes of an intake manifold 110 of the engine in the present instance. For instance, in a case of a four cylinder engine, four opening and closing members 100 a are placed in four tubes, respectively, of the intake manifold 110, and the single valve drive shaft 100 b extends through the lower end portions of the opening and closing members 100 a to integrally drive the opening and closing members 100 a in a valve closing direction CL or a valve opening direction OP to control the intake air supplied from the intake manifold 110 to combustion chambers (located on the left side in FIG. 7) of the engine. In the following description, only one of the opening and closing members 100 a along with the valve drive shaft 100 b will be described for the sake of simplicity.

The variable air intake system includes the above described valve 100 as well as an electric motor 1, a speed reducer 2 and a clutch 3 shown in FIG. 3A. The motor 1 is rotatable in a forward direction or a reverse direction upon energization thereof (in an energized state). The speed reducer 2 reduces the rotational speed of the rotation transmitted from the motor 1 and outputs the rotation of the reduced rotational speed from an output shaft 24 to the valve drive shaft 100 b of the valve 100 to drive the same. The clutch 3 is interposed between the motor 1 and the speed reducer 2. The energization of the motor 1 is controlled by a control device (such as an electronic control unit that is abbreviated as ECU).

As discussed above, the valve 100 has the hinged valve structure, in which the valve drive shaft 100 b is provided at one side of the plate-shaped opening and closing member 100 a that is configured and positioned to limit an increase in a resistance of the air in the air intake passage 111 at the time of full opening of the valve 100.

Now, the basic structure of the clutch 3 will be described.

With reference to FIGS. 2A to 3B, the clutch 3 includes a driving-side rotator 4, a driven-side rotator 5, an annular collar 6 and a plurality of rollers (serving as engageable elements) 7. The driving-side rotator 4 is rotated by the rotational force of the motor 1. The driven-side rotator 5 is driven by the driving-side rotator 4 through circumferential engagement therebetween. An inner circumferential surface 8 of the collar 6 is coaxially placed relative to the driving-side rotator 4 and the driven-side rotator 5. The rollers 7 are radially placed between the driven-side rotator 5 and the collar 6. The respective components of the clutch 3 may be made of metal or rigid resin.

The collar 6 of the present embodiment is configured into a cylindrical body, which is placed radially outward of the driving-side rotator 4 and the driven-side rotator 5 to surround the same. The inner circumferential surface 8 of the collar 6 serves as an engaging surface and extends along an imaginary circle, a center of which coincides with the rotational axis of the driving-side rotator 4 and of the driven-side rotator 5. The collar 6 is non-rotatably fixed to a clutch housing 9.

In the present embodiment, although the collar 6 is installed in the clutch housing 9, the collar 6 may be formed integrally with the clutch housing 9.

The driven-side rotator 5 is coupled with an input shaft (an output side of the clutch 3) 11 of the speed reducer 2 and has one or more (three in this embodiment) fan shaped-portions (engaging portions) 12, each of which extends radially outward. A radially outer surface 13 of each fan-shaped portion 12 is a planar surface that is generally parallel to a tangential direction, which is tangential to the cylindrical inner circumferential surface 8 of the collar 6.

With the above construction, a radial gap G is defined between the radially outer surface 13 of each fan-shaped portion 12 of the driven-side rotator 5 and the inner circumferential surface 8 of the collar 6. In the gap G, one large radial gap (circumferentially intermediate gap section) L1 and two small radial gaps (first and second circumferential side gap sections) L2 are radially defined between the radially outer surface 13 of each fan-shaped portion 12 of the driven-side rotator 5 and the inner circumferential surface 8 of the collar 6. The small radial gaps L2 are located on opposed circumferential sides, respectively, of the large radial gap L1. A radial size (radial extent) of each of the small radial gaps L2 is smaller than that of the large radial gap L1.

Each roller 7 is configured into a cylindrical body and is placed in the gap G, i.e., is radially placed between the radially outer surface 13 of the corresponding fan-shaped portion 12 and the inner circumferential surface 8 of the collar 6. A corresponding holder 14 rotatably holds the roller 7 at opposed circumferential sides of the roller 7 and is rotatable relative to the driven-side rotator 5 about the rotational axis of the driven-side rotator 5.

An outer diameter (a radial size) L3 of the roller 7 is smaller than the radial size of the large radial gap L1 and is larger than the radial size of the small radial gap L2. That is, the outer diameter L3 of the roller 7, the radial size of the large radial gap L1 and the radial size of the small radial gap L2 are set to satisfy the relationship of L1>L3>L2. In this way, the roller 7 is always retained in the gap G between the radially outer surface 13 of the fan-shaped portion 12 of the driven-side rotator 5 and the inner circumferential surface 8 of the collar 6.

When the roller 7 is placed in a location, at which the radial distance between the radially outer surface 13 of the fan-shaped portion 12 and the inner circumferential surface 8 of the collar 6 is larger than the outer diameter of the roller 7, the driven-side rotator 5 can rotate relative to the collar 6. Furthermore, when the roller 7 is placed in another location, at which the radial distance between the radially outer surface 13 of the fan-shaped portion 12 and the inner circumferential surface 8 of the collar 6 coincides with the outer diameter L3 of the roller 7, the roller 7 is securely held between the radially outer surface 13 of the fan-shaped portion 12 and the inner circumferential surface 8 of the collar 6. That is, the driven-side rotator 5 is locked to the collar 6 through the rollers 7, and thereby the rotation of the driven-side rotator 5 is prevented by the collar 6, which is securely held.

The driving-side rotator 4 is securely engaged or connected with an output shaft (an input side of the clutch 3) of the motor 1 to rotate integrally therewith and has a plurality (three in this embodiment) of fan-shaped portions 16. In this way, when the driving-side rotator 4 is rotated by the motor 1, the fan-shaped portions 16 of the driving-side rotator 4 abut against the fan-shaped portions 12, respectively, of the driven-side rotator 5 in the circumferential direction to conduct the rotational force of the driving-side rotator 4 to the driven-side rotator 5.

Two engagement releasing projections 17 project circumferentially outward from two opposed circumferential ends, respectively, of each fan-shaped portion 16 of the driving-side rotator 4. In a state where each fan-shaped portion 16 of the driving-side rotator 4 abuts against the corresponding fan-shaped portion 12 of the driven-side rotator 5, the engagement releasing projection 17 pushes the corresponding holder 14 toward the large radial gap L1 to displace the corresponding roller 7, which is supported by the holder 14, toward the large radial gap L1. Specifically, the roller 7 is moved to the location where the radial distance between the radially outer surface 13 of the fan-shaped portion 12 of the driven-side rotator 5 and the inner circumferential surface 8 of the collar 6 is larger than the outer diameter L3 of the roller 7 to enable rotation of the roller 7 between the fan-shaped portion 12 of the driven-side rotator 5 and the collar 6.

The speed reducer 2 is a speed reducer of a gear type and will be described with reference to FIGS. 3A and 3B. The speed reducer 2 of the present embodiment includes a worm 21, an intermediate gear 22 and a final gear 23. The worm 21 is rotated integrally with the driven-side rotator 5. The intermediate gear 22 is meshed with the worm 21 and is driven by the worm 21. The final gear 23 is meshed with the intermediate gear 22 and is driven by the intermediate gear 22. The output shaft 24, which is provided in the final gear 23, is connected to the valve drive shaft 100 b to drive the same.

Now, a basic operation of the clutch 3 will be described.

When the motor 1 is rotated in the forward direction or the reverse direction through the control operation of the energization of the motor 1, the rotational force of the motor 1 conducted to the driving-side rotator 4 causes the corresponding one of the engagement releasing projections 17 of each fan-shaped portion 16 of the driving-side rotator 4 to push the corresponding roller 7 through the corresponding holder 14 toward the corresponding large radial gap L1. In this way, the driving-side rotator 4 and the driven-side rotator 5 together with the collars 7 are permitted to rotate freely relative to the collar 6. Then, when the rotational force of the driving-side rotator 4 is conducted to the driven-side rotator 5 upon abutment of the driving-side rotator 4 to the driven-side rotator 5, the driven-side rotator 5 is rotated together with the driving-side rotator 4. The rotational speed of the driven-side rotator 5 is reduced through the speed reducer 2, and the rotation of the speed reducer 2 at the reduced rotational speed is outputted through the output shaft 24 to change the opening degree of the valve 100.

When the opening degree (the rotational angular position) of the valve 100 reaches the target opening degree (the target rotational angular position) of the valve 100, the energization of the motor 1 is stopped (i.e., the motor 1 in a de-energized state). In this state, for example, when a rotational load is manually applied to the valve 100 to apply a rotational force to the driven-side rotator 5, each roller 7 is clamped, i.e., is securely held between the driven-side rotator 5 and the collar 6 upon a slight rotational movement of the driven-side rotator 5. Thus, the driven-side rotator 5 is securely locked to the collar 6 through the rollers 7. Therefore, the driven-side rotator 5 becomes non-rotatable, and thereby the rotation of the valve 100 is limited.

However, the pressure pulsation, which occurs in the intake passage, causes application of a rotational force (specifically, a rotational force caused by large vibration, large load, large pressure pulsation or the like) to the valve 100. Particularly, in the case of the present example, in which the hinged valve structure is adapted, a very large pressure pulsation is applied to the valve drive shaft 100 b. Then, the rotational force, which is caused by this pressure pulsation, is conducted to the driven-side rotator 5 through the speed reducer 2, so that the locked state of each roller 7 may possibly be released. That is, the rotation of the valve 100 may not be effectively limited by the clutch 3.

In view of the above point, the following technique is adapted in the present embodiment to increase the holding capability of the clutch 3 for holding the valve 100 in place (in the selected angular position).

Specifically, the inner circumferential surface 8 of the collar 6 of the clutch 3 has a plurality of recesses, each of which is capable of limiting the movement and rotation of the corresponding one of the rollers 7 in the urged state of the roller 7.

The recesses of the present embodiment are formed as grooves 25, into each of which the corresponding roller 7 can be lightly fitted (engaged). Each groove 25 extends parallel to the axis of the roller 7. As shown in FIG. 2B, a cross section of each groove 25 may have an arcuate shape that forms an arcuate surface having a curvature (or a radius of curvature), which may generally coincide with or may be larger (substantially or slightly larger) than or smaller (substantially or slightly smaller) than that of the cylindrical outer surface (circular cross section) of the roller 7. Furthermore, the cross section of the groove may have any other shape, which is other than the arcuate shape. For example, the cross section of the groove may be configured into a rectangular shape, a triangular shape (including moderately tilted surfaces) or the like.

The number of the grooves 25 is, for example, nine in this instance and may be increased or decreased depending on a need. The grooves 25 are arranged one after another at generally equal angular intervals along the inner circumferential surface 8 of the collar 6.

As described above, the grooves 25 are provided in the inner circumferential surface 8 of the collar 6, so that each roller 7 can be fitted (engaged) into the corresponding groove 25 in the de-energized state of the motor 1. As a result, the roller 7 can be strongly locked (engaged) to the collar 6 through the groove 25 in the de-energized state of the motor 1, and thereby the rotation of the driven-side rotator 5 cab be limited without fully relying on the frictional force between the roller 7 and the collar 6. Therefore, the change in the opening degree (the change in the rotational position) of the valve 100 caused by the pressure pulsation can be advantageously limited.

At the time of driving the motor 1 to rotate the driving-side rotator 4 in the forward direction or the reverse direction, the corresponding engagement releasing projection 17 of each fan-shaped portion 16 of the driving-side rotator 4 circumferentially pushes the corresponding roller 7 toward the large radial gap L1 to release the locking of the roller 7. Then, when the driving-side rotator 4 circumferentially abuts against the driven-side rotator 5 to conduct the rotational force of the driving-side rotator 4 to the driven-side rotator 5, the opening degree (the rotational position) of the valve 100 is adjusted, i.e., is changed.

The variable air intake system is required to set the opening degree of the valve 100 within an effective opening degree range thereof, which enables an improvement of the fuel consumption of the engine.

(a) Specifically, when the opening degree of the valve 100 is reduced, the pumping loss is increased to cause the deterioration of the fuel consumption (see FIG. 4).

(b) In contrast, when the opening degree of the valve 100 is reduced to cause generation of the swirl flow in the combustion chamber, the fuel combustion state is improved to improve the internal (external) limit exhaust gas recirculation (EGR) ratio. That is, when the EGR ratio at the time of operating the engine with the small opening degree of the valve 100 is increased, the cooling loss and the pumping loss are reduced to obtain the fuel consumption improving effect (see FIG. 5).

Because of the relationship between the item (a) and the item (b) discussed above, there exists a predetermined effective opening degree range of the valve 100 for obtaining the fuel consumption improving effect (see FIG. 6). That is, when the valve 100 is driven out of the predetermined opening degree range toward the fully closed position thereof, the effect of the fuel consumption deteriorating rate caused by the pumping loss becomes larger than the fuel consumption improvement caused by the EGR. Thereby, as a whole, the fuel consumption is deteriorated. In contrast, when the valve 100 is driven to increase the opening degree of the valve 100 beyond the predetermined opening degree range, the fuel consumption improving effect of the EGR cannot be obtained, so that the fuel consumption is deteriorated as a whole.

As described above, there exists the effective opening degree range of the valve 100, within which the fuel consumption of the engine can be improved. In the variable air intake system, it is required to set the opening degree of the valve 100 within this effective opening degree range of the valve 100, which enables the improvement of the fuel consumption.

In order to maintain the opening degree of the valve 100 within the effective opening degree range of the valve 100, the circumferential locations of the grooves 25 are set as follows. In the following description, only one of the rollers 7 of the clutch 3 and its associated grooves 25 will be described with reference to the valve 100 for the sake of simplicity.

The clutch 3 and the valve 100 are synchronized to satisfy the following conditions. That is, with reference to FIG. 1, when the driving-side rotator 4 is rotated to rotate the driven-side rotator 5 and thereby to place the roller (more specifically, a circumferential center or a location adjacent thereto of the roller) 7 in an optimum angular position (first angular position) Z along the circumferential surface 8 of the collar 6, the valve 100 is placed in a most effective valve angle θ, at which the fuel consumption improving effect (the fuel consumption improving rate) of the intake air supplied from the valve 100 to the engine through the air intake passage 111 is maximized. When the driving-side rotator 4 is rotated to rotate the driven-side rotator 5 and thereby to displace the roller (more specifically, the circumferential center or the location adjacent thereto of the roller) 7 in one circumferential direction from the optimum angular position Z to a valve closing side least effective angular position (second angular position) e1 along the circumferential surface 8 of the collar 6, the valve 100 is rotated in a valve closing direction from the most effective valve angle θ to a valve closing side least effective valve angle f1, at which the fuel consumption improving effect of the intake air supplied from the valve 100 to the engine through the air intake passage 111 is reduced to zero. When the driving-side rotator 4 is rotated to rotate the driven-side rotator 5 and thereby to displace the roller (more specifically, the circumferential center or the location adjacent thereto of the roller) 7 in an opposite circumferential direction, which is opposite from the one circumferential direction, from the optimum angular position Z to a valve opening side least effective angular position (third angular position) e2 along the circumferential surface 8 of the collar 6, the valve 100 is rotated in a valve opening direction from the most effective valve angle θ to a valve opening side least effective valve angle f2, at which the fuel consumption improving effect of the intake air supplied from the valve 100 to the engine through the air intake passage 111 is reduced to zero.

One (serving as a valve closing side engaging recess or groove) of the grooves 25 is formed at a corresponding angular position x, more specifically a circumferential center or a location adjacent thereto of the valve closing side engaging groove 25 is placed at the corresponding angular position x in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve closing side least effective angular position e1 and is engageable with the roller 7 to securely hold the roller 7 in cooperation with the fan-shaped portion 12 of the driven-side rotator 5 in the de-energized state of the electric motor upon application of the rotational force from the valve 100 to the driven-side rotator 5. Another one (serving as a valve opening side engaging recess or groove) of the grooves 25 is formed at a corresponding angular position y, more specifically a circumferential center or a location adjacent thereto of the valve opening side engaging groove 25 is placed at the corresponding angular position y in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve opening side least effective angular position e2 and is engageable with the roller 7 to securely hold the roller 7 in cooperation with the fan-shaped portion 12 of the driven-side rotator 5 in the de-energized state of the motor 1 upon application of the rotational force from the valve 100 to the driven-side rotator 5. In addition, another one (serving as an optimal position engaging recess or groove) of the grooves 25 is formed at the optimal angular position Z, more specifically, the circumferential center or the location adjacent thereto of the optimal position engaging groove 25 is placed at the optimum angular position Z in the circumferential surface 8 of the collar 6 to securely hold the roller 7 in cooperation with the fan-shaped portion 12 of the driven-side rotator 5 in the de-energized state of the motor 1 upon application of the rotational force from the valve 100 to the driven-side rotator 5.

Here, although only one valve closing side engaging groove 25 is formed in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve closing side least effective angular position e1, and only one valve opening side engaging groove 25 is formed in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve opening side least effective angular position e2. However, it is possible to provide more than one valve closing side engaging groove 25 between the optimum angular position Z and the valve closing side least effective angular position e1 and more than one valve opening side engaging groove 25 between the optimum angular position Z and the valve opening side least effective angular position e2.

Furthermore, a speed reduction ratio G of the speed reducer 2 satisfies relationships of γ1/G≦α and γ2/G≦β to implement the above locations of the valve closing side engaging groove 25 and of the valve opening side engaging groove 25. Here, the speed reduction ratio G is a ratio between the rotational speed of the input side (the input shaft 11) of the speed reducer 2 and the rotational speed of the output side (the output shaft 24) of the speed reducer 2. In other words, the speed reduction ratio G indicates the number of rotations of the input side (the input shaft 11) of the speed reducer 2 per rotation of the output side (the output shaft 24) of the speed reducer 2. Here, γ1 denotes an angular difference between the optimum angular position Z and the angular position x of the valve closing side engaging groove 25 along the circumferential surface 8 of the collar 6, and a denotes an angular difference between the most effective valve angle θ and the valve closing side least effective valve angle f1. Also, γ2 denotes an angular difference between the optimum angular position Z and the angular position y of the valve opening side engaging groove 25 along the circumferential surface 8 of the collar 6, and 3 denotes an angular difference between the most effective valve angle θ and the valve opening side least effective valve angle f2. In this instance, since the angular difference γ1 and the angular difference γ2 are the same (γ), the above relationships may be expressed as γ/G≦α and γ/G≦β. Through use of the above relationships, it is easy to set the above locations of the valve closing side engaging groove 25 and of the valve opening side engaging groove 25 within the range of the angular difference γ1 and the angular difference γ2, respectively, without knowing the location of the valve closing side least effective angular position e1 or the location of the valve opening side least effective angular position e2 even in the case where the most effective valve angle θ varies from one model to another model as long as the speed reduction ratio G and the angular difference α, β are known.

The above embodiment provides the following advantages.

With the above construction of the variable air intake system, at least one valve closing side engaging groove 25 is formed in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve closing side least effective angular position e1, and at least one valve opening side engaging groove 25 is formed in the circumferential surface 8 of the collar 6 between the optimum angular position Z and the valve opening side least effective angular position e2. Therefore, it is possible to reliably hold the valve 100 within the effective opening degree range (the range between the valve closing side least effective valve angle f1 and the valve opening side least effective valve angle f2) of the valve 100, which enables the improvement of the fuel consumption of the engine.

That is, even when the large vibration, the large load and/or the large pressure pulsation applied to the valve 100 is conducted to the driven-side rotator 5 through the speed reducer 2, the roller 7 can be securely engaged in the corresponding groove 25 located between the valve closing side least effective angular position e1 and the valve opening side least effective angular position e2, so that the roller 7 can be more securely held between the groove 25 of the collar 6 and the fan-shaped portion 12 of the driven-side rotator 5 to limit the displacement of the roller 7 to fix the opening degree of the valve 100 within the effective opening degree range.

In the above embodiment, the speed reducer 2 is placed only between the clutch 3 and the valve 100. Alternatively, an additional speed reducer may be placed between the motor 1 and the clutch 3 besides the above speed reducer 2.

The number of the recesses (e.g., the grooves 25 or the tilts) is set such that the two grooves are provided at the corresponding locations on the valve closing side and the valve opening side, respectively, of the optimum angular position Z to achieve the conditions of γ1/G≦α and γ2/G≦β. However, the number of the recesses (e g., the grooves 25, the tilts) may be further increased from the above number. That is, the recesses (e.g., the grooves 25 or the tilts) may be provided one after another at the equal angular intervals of the angle γ in a manner that satisfies conditions of γ/G≦α and γ/G≦β.

In the above embodiment, the hinged valve 100 is used. In place of the hinged valve, a butterfly valve (e.g., a butterfly valve, which has a circular valve plate and a valve drive shaft extending through a center of the circular valve plate in a direction parallel to a plane of the circular valve plate) may be used. Also, the valve of the present invention may be used as any other types of valves (e.g., a throttle valve), if desired.

In the above embodiment, the radially outer surface 13 of each fan-shaped portion 12 is the planar surface. Alternatively, an engaging groove, which has an arcuate cross section and extends in the axial direction of the driven-side rotator 5, may be formed in the radially outer surface 13 of each fan-shaped portion 12 in such a manner that the engaging groove of the radially outer surface 13 is engageable with the corresponding roller 7.

In the above embodiment, each roller 7 is held by the corresponding holder 14. Alternatively, the holder 14 may be eliminated.

In the above embodiment, the cylindrical roller 7 is used as the example of the engageable element. Alternative to the roller 7, any other type of rotatable or rollable element (e.g., a spherical ball) may be used as the engageable element. The outer shape of the rotatable element is not necessarily circular. For instance, the outer shape of the rotatable element may be ellipsoidal or the like, which resists smooth rotation thereof. Furthermore, the engageable element is not necessarily the rotatable element. For example, the engageable element may be a slidable element, which is slidable between the driven-side rotator 5 and the collar 6.

In the above embodiment, the collar 6 is placed radially outward of the driving-side rotator 4 and the driven-side rotator 5. Alternatively, the collar 6 may be placed radially inward of the driving-side rotator 4 and the driven-side rotator 5. In such a case, the outer circumferential surface of the collar 6 serves as the circumferential surface that is engageable with the engageable elements (e.g., the rollers 7). Thus, the recesses (e.g., the grooves 25 or the tilts) may be provided in the outer circumferential surface of the collar 6.

In the above embodiment, the driving-side rotator 4 and the driven-side rotator 5 make the surface contact therebetween. Alternatively, the driving-side rotator 4 and the driven-side rotator 5 may make a point contact, a line contact or the like therebetween.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A variable air intake system for an internal combustion engine, comprising: an electric motor that is rotated to generate a rotational force in an energized state of the electric motor; a valve that is placed in an air intake passage of the internal combustion engine and is rotated by the rotational force transmitted from the electric motor to adjust intake air supplied to the internal combustion engine through the air intake passage; and a clutch that is placed between the electric motor and the valve to enable transmission of the rotational force from the electric motor to the valve and to disable transmission of a rotational force from the valve to the electric motor, wherein: the clutch includes: a driving-side rotator that is rotated by the rotational force transmitted from the electric motor and includes a plurality of circumferential side engagement releasing projections, each of which circumferentially projects from a corresponding adjacent part of the driving-side rotator that is adjacent to the circumferential side engagement releasing projection; a driven-side rotator that is coaxial with the driving-side rotator and is rotated by the driving-side rotator upon circumferential engagement with the driving-side rotator to rotate the valve in the energized state of the electric motor; an annular collar that is non-rotatably held and has a circumferential surface, which is coaxial with the driven-side rotator, wherein a radial gap is formed between an engaging portion of the driven-side rotator and the circumferential surface of the collar and includes first and second circumferential side gap sections and a circumferentially intermediate gap section, which are arranged in such a manner that the circumferentially intermediate gap section is circumferentially placed between the first and second circumferential side gap sections and has a radial size larger than a radial size of any of the first and second circumferential side gap sections; and an engageable element that is circumferentially placed between the first and second circumferential side gap sections in the radial gap, wherein a radial size of the engageable element is smaller than the radial size of the circumferentially intermediate gap section and is larger than the radial size of any of the first and second circumferential side gap sections, and the engageable element is circumferentially displaceable by a corresponding one of the plurality of circumferential side engagement releasing projections at a time of driving the driven-side rotator by the driving-side rotator; the clutch and the valve are synchronized to satisfy all of the following conditions: when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to place the engageable element in a first angular position along the circumferential surface of the collar, the valve is placed in a most effective valve angle, at which a fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is maximized; when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to displace the engageable element in a first circumferential direction from the first angular position to a second angular position along the circumferential surface of the collar, the valve is rotated in a valve closing direction from the most effective valve angle to a valve closing side least effective valve angle, at which the fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is reduced to zero; and when the driving-side rotator is rotated to rotate the driven-side rotator and thereby to displace the engageable element in a second circumferential direction, which is opposite from the first circumferential direction, from the first angular position to a third angular position along the circumferential surface of the collar, the valve is rotated in a valve opening direction from the most effective valve angle to a valve opening side least effective valve angle, at which the fuel consumption improving effect of the intake air supplied from the valve to the internal combustion engine through the air intake passage is reduced to zero; a valve closing side engaging recess is formed in the circumferential surface of the collar between the first angular position and the second angular position and is engageable with the engageable element to securely hold the engageable element in cooperation with the engaging portion of the driven-side rotator in the de-energized state of the electric motor; and a valve opening side engaging recess is formed in the circumferential surface of the collar between the first angular position and the third angular position and is engageable with the engageable element to securely hold the engageable element in cooperation with the engaging portion of the driven-side rotator in the de-energized state of the electric motor.
 2. The variable air intake system according to claim 1, further comprising a speed reducer that is placed between the electric motor and the valve to reduce a rotational speed of rotation, which is originated from the electric motor and is conducted to the speed reducer, wherein a speed reduction ratio G of the speed reducer satisfies relationships of γ1/G≦α and γ2/G≦β where: γ1 denotes an angular difference between the first angular position and an angular position of the valve closing side engaging recess along the circumferential surface of the collar; α denotes an angular difference between the most effective valve angle and the valve closing side least effective valve angle; γ2 denotes an angular difference between the first angular position and an angular position of the valve opening side engaging recess along the circumferential surface of the collar; and β denotes an angular difference between the most effective valve angle and the valve opening side least effective valve angle.
 3. The variable air intake system according to claim 1, wherein: the collar is placed radially outward of the driving-side rotator and the driven-side rotator; and the circumferential surface of the collar is an inner circumferential surface of the collar.
 4. The variable air intake system according to claim 1, wherein the engageable element is a roller, which is rollable along the circumferential surface of the collar.
 5. The variable air intake system according to claim 4, wherein each of the valve closing side engaging recess and the valve opening side engaging recess is in a form of a groove, into which a portion of an outer peripheral surface of the roller is engageable.
 6. The variable air intake system according to claim 1, wherein: the engageable element has a circular cross section; each of the valve closing side engaging recess and the valve opening side engaging recess has an arcuate surface; and a radius of curvature of the arcuate surface of each of the valve closing side engaging recess and the valve opening side engaging recess is generally the same or slightly larger than that of the circular cross section of the engageable element.
 7. The variable air intake system according to claim 1, wherein an optimal position engaging recess is formed in the circumferential surface of the collar at the first angular position and is engageable with the engageable element to securely hold the engageable element in cooperation with the engaging portion of the driven-side rotator in the de-energized state of the electric motor.
 8. The variable air intake system according to claim 1, wherein: the engageable element is positionable in a securely engaged state when the engageable element is circumferentially moved from the circumferentially intermediate gap section toward one of the first and second circumferential side gap sections and is securely held between the engaging portion of the driven-side rotator and the circumferential surface of the collar upon rotation of the driven-side rotator induced by the rotational force transmitted from the valve in a de-energized state of the electric motor; and the engageable element is positionable in a released state when the engageable element held in the securely engaged state is circumferentially pushed by one of the plurality of circumferential side engagement releasing projections of the driving-side rotator toward the circumferentially intermediate gap section to release the engageable element from the securely engaged state and thereby to permit integral rotational movement of the driving-side rotator, the driven-side rotator and the engageable element in the energized state of the electric motor. 